vasprintf: return -1 on strdup failure

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
fdisk_sun: fix corrupted partition data with blank disk

After creating Sun disk label for the first time for a blank disk,
the partition table appears corrupted because current_label_type will
never get set to a proper type. Fix this by calling check_sun_label()
after BusyBox has created the label.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
fdisk_sun: fix partition alignment

When the display unit is sectors, the partition alignment will convert
the partition start to a wrong unit (it should always be in sectors). Fix
this.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>